Wire grid polarizers are widely used in devices for graphic information imaging (e.g., see U.S. Pat. No. 6,452,724, incorporated herein by reference). The commonly-used technology for manufacturing these devices is based on optical or interference lithography. However, the cost associated with the use of the tools designed for these applications is considered very significant. The existing approach and tools make it difficult to scale the production from smaller semiconductor wafer sizes to larger area substrates (such as glass sheets or plastic). In addition, the existing approach makes it is very difficult to create wire grid structures with a period of 150 nm or less. While different applications have different requirements, structures with smaller feature size are usually associated with higher performance.
A method for nanorelief formation on a film surface, comprising plasma modification of a wave ordered nanostructure (WOS) formed on amorphous silicon layer, was disclosed in Russian Patent Application RU 2204179, incorporated herein by reference.
This approach is schematically illustrated on FIG. 1. It includes the following steps. First, a layer of amorphous silicon 102 is deposited on top of the target thin film layer 101. Then, this silicon layer is sputtered with a flow of nitrogen ions so as to create an array of wave ordered nanostructures. The resultant wave-ordered nanostructure comprises relatively thick regions of amorphous silicon nitride 103 and relatively thin regions of amorphous silicon nitride 104 situated respectively on the front and back sides of the wave structure 104. As shown, the wave troughs are spaced from the surface of the film layer 101 by a distance D equal to about one third of the nanostructure wavelength (λ). After the wave-ordered nanostructure is formed, its planar pattern is transferred into the underlying film layer 101 by selectively etching the amorphous silicon layer 102 while using regions 103 and 104 as a nanomask.
However, experiments using nanostructures obtained by oblique sputtering of amorphous silicon with nitrogen ions (N2+-Si system) showed that these structures often do not possess a desired degree of natural ordering (i.e., high coherency). FIG. 2 shows an array of nanostructures manufactured by this technique. The figure shows that even in a relatively small area this array has a significant number of defects. It may not be sufficiently coherent enough for optoelectronic applications.